Page:The Kinematics of Machinery.djvu/542

 520 KINEMATICS OF MACHINERY.

a special regulator, in the form of a fly, is attached to the striking gear. The weight drums are connected to their spindles by running clicks, so that they may be moved backwards by hand in order to bring the weights once more into such a position that they can drive the machine. In reality these clicks are simply auxiliary mechanisms for the purpose of supplying the machine anew with its driving organ. There is lastly a lever which can be moved by hand so as to throw the striking-train in or out of gear ; this lever with its connections form a directing-train moveable by hand. Summing up the different mechanisms which together form such a clock as we have described, we find them to be eight in number, two main-trains, a self-acting director, a hand-director, two supply- trains worked by hand, and two regulating-trains ; five of them are automatic and the others arranged for being moved by hand.

A saw-frame, which we may suppose to be driven by a belt from some prime-mover, has its main-train in the crank and connecting- rod mechanism (C^'P- 1 -)*, which drives the frame. The tool (the saw-blade) forms part of the block c ; the work-piece is the block or tree-trunk being sawn. The tool forms upon this its envelope, the saw-cut, removing for this purpose those portions of material which are presented to it at each stroke. The motion of the work- piece by which this is done is effected by a ratchet-train driven from the crank-shaft and moving forward periodically the frame or table upon which the log rests. This train therefore forms the supply. The only regulator is the stop-gear, which enables the workman to place the driving-belt upon a loose pulley.

In the Jacquard loom there are two main-trains, the me- chanisms for working the beam and the shuttle ; the Jacquard mechanism itself forms a very complex directing-gear. There is also a supply-gear for moving the chain forward and a regulator (already mentioned) for the tension of the warp, and lastly one or more stopping arrangements.

The hydraulic ram, which we have had occasion to mention several times, forms a very easy subject for descriptive analysis. The head water HA B, Fig. 361, is the driver, while the prolonga- tion, D E, of the same column, forms the work-piece, both being enclosed in suitable vessels. The main-train is a ratchet-train having two pawls in the valves JTand D. There is no director, the air-vessel E forms a regulator.